Signal measuring system



Feb. "6, 1940. s. B. HUGHES SIGNAL MEASURING SYSTEM Filed Sept. 8, 1938 BY .Hy/

w m m m m m W3 my w H w m m m5 N Mr H m .,.Q O4 1 V m w 1% ATTORNEY v PatentedFeb.6,1 94O I b 2.189111 SIGNAL MEASURING sys'rEM 7 Samuel Bettle Hughes, Omaha, Nebn, assignor to American Telephone and Telegraph Company,

' a corporation of New York Application September8, 1938 Seriallio. 228,997.

sclei s. 01. na -175.1

I T T This invention relates to electrical Signaling subscriberscircuit, may be connected through a systems. More particularly this invention re double-pole single-throw switch S1 to, the prilates to electrical systems for indicating the mary winding of the transformer T1, the seconde level of speech or other currents. ary winding of which is connected as part of the 5 When speech or other energy is impressed upgrid circuit of an amplifier tube V1. An elec- I;

on the telephone transmitter of a telephone subtrical buzzer Y of any well known type, having a scribers set it is difficult, and often impossible, sourceoffcurrent forits operation as shown, may for the speaker or operator to determine whether be positioned directlyin front of the transmitter the level of the-impressed energy is sufiicient for TR. so that sounds prcducedby the buzzer and good transmission. Two factors primarily de-z impressed upon the transmitter 'IR may be trans- 1Q termine whether or not the impressed energy is mitted to the grid circuit of tube V1. .The switch sufficient for good transmissionto the distant S1 hence may be employed for connecting the end of the circuit. fI'hesetwo factors are (l) telephonetransmitter TR to the circuits of the the distance between the speakerslips and the amplifier tube V1 so that either voice energy or telephone transmitter and .(2) the tone or level the buzzer energy impressed upon the transmitter of thevoice used. 7 v -TR, may be-transmitted and amplified, the am- Speech or other energy of loud tone or high plified energy beingthen utilized for obtaining level need not be impressed as closely to the an indication of the level of the impressed en telep e transmitter e y of owe e ergy as will be described more fully hereinafter. 2 or level to produce the same electrical effects. v 'Ihemeasuringapparatus for determining the' A very lowtone or signal level will necessarily level oft-the energy impressedupon the grid cirhave to be impressed q e l y 0* the l cuit of the amplifier tube V1 includes afgeneraphone transmitter to be effectively transmitted torr of alternating rrent designated G which to the distantstation. If a low tone is produced maybe an ordinary 60 cycle alternating current a substantial distance from the transmitter in generator of 110 or 1.15 lt which b n. y of Course, be attenuated by the Circuit nected by a double-pole single-throw switch S2 as to be practically, inaudible at the distant end. t th primary winding of a transformer T2 The determination of theproper tone level and/or through-one d 1 another double-p019 Single-h h p p r distance b tw the sp t lips throw switch s3. When both of the switches s2 30 and the telephone transmitter is of importance hndyss r d d-th 1a L will b lighted and to the eflicient use of signaling systems employed will therefore indicate that the current of the for telephone transmission; v t generator G is being transmitted to the measur It is, therefore, one of-the objects of this ining apparatus f th invention. H vention to indicate instantly 130' the subscriber The transformer T2. has four secgndary wind-r 35 or operator the level of speech orother signal ings, one of which, designated W1, is connected e r y impressed u telephone transmitter t the filament of the amplifying tube v1 as well wh f r xamp may D p t o a t l p e as to the filaments of two rectifying tubes veend substation circuit. a l V3,-the latter filaments being arranged in parallel It is a further, object of this inventionto indirelationship, The secondary winding We of 4 40 cate instantly to the speaker or operator whether transformer T2 i t d t th tw plate t e level o Speech 1 t Signal energy is Slime ielectrodes of a full wave rectifying tube V4 which Cient for good transmissioni has two filaments, these twofilaments being ar It is a still further object of this invention to ranged in series relationship and being supplied indicate approximately what thelevel of'theem ith energy by th secondary winding We of the er y impressed up e n ter s w en t e transformer T2. The t fourth'secondary winding 45 source of the energy ispositioned at di-iferent We of transformer T2 will be employed to heat distances from the transmitter. 2 l the filaments of lamps Lr Lz and L3' in a manner These and other objectsand features oi the: t be described more fully hereinafter. invention will be better: understood from the de Y i A potentiometer P receives the current rectitailed description hereinafter following when fled by the. tube V The upper t rmi al ofth read in connection with the accompanying drawpotentiometer P is connected to the midpoint ins illustrat n one m ment of th ,ip-ven lof th windingWz of. transformer T2.- The lower tion given merely for the purposes of illustration terminal of the potentiometer P is connected to .Referring tothe drawing,- the telephone transthe filament circuit of the tube V4 through a 5 mitter TR, which may be a part era telephone coil D, this coil .beingpartot a low pass filter 'currents to various circuits of the apparatus of this invention, as will be described hereinafter.

The amplifler'tube V1 is of the heater type,

the cathode of which is in circuit with a resistor Z1, the secondary winding of transformer T1 and the grid of the tube V1, the latter circuit being commonly known as the grid circuit of the tube. The plate circuit of the tube V1 includes the primary winding of transformer T3, that portion of potentiometer P between adjustable contacts, K1 and K2, the winding W1 of'transforme'r T2,and

the filament of the tube V1. The energy;-ampli- I fled by the tube V1 is impressed upon the grids of both of the tubes V2 and V3 arranged in paral lel relationship, the grid circuits of these tubes including the secondary winding of the transformer T3 and a condenser'Ca'. The contact K2 of the potentiometer -P maybe adjusted for changing the bias of the grid electrodes of both tubes to any desired operating value. The plate electrodes of the tubes V2 and V3 are both connected in circuit with relay apparatus which will now be described.

The plate electrodes of tubes V2 and V3 are tied together and are connected in series circuit witha milliammeter MA, a resistor Z3, a resistor Z2, the winding of relay R1,'that portion of the potentiometer P' between the lower terminal of the potentiometer and the terminal-K2, the secondary winding W of transformer T2, and the filamentsof tubes V2 and V3. The winding of 4d relay R1 is shunted by condenser C4 so that all of the direct current flowing in the series circuit just described will be by-passed through this relay winding.

Ifthe impressed energy causes current toflow in this series circuit at a very low value it maybe suflicient to operate the relay R1 but the voltages impressed across resistors Z2 and Z3 will be insufficient to operate the relays R2 and R3,

the windings of' which shunt th'es'e resistors re' spectively.

v I If a greater current is rectified by tubes V2' and'Va, the voltage impressed across re-" 'sistor Z2 maybe suflicient to-operate the relay R2 and this current will also flow through-the winding of relay R1 and maintain the latter rea lay operated." If a still greater current is rectifled by tubes V2 and V3;"the voltage across re-' sistor Z3 may 'be suflicient to operate therelay R and both relays R1 and R2 will be maintained inoperated condition. Of course, the current flowing through this series circuit will be'insufficient to operate any one of therelays R1,'R2 and R3 when no speech or other energy is im- Dressed upon the transmitter TR. I The operation of relay R1 will in turn operat the relay" R1," thecircuit of the winding of relay R'i including "the battery E1, the lower blade of" 1 the switch S the armature and contact of relay R1, the' winding of relay R'1, and resistor Z11." The operationof relay R2 will: cause the operation of'relay R current flowing from battery 'B1. over the circuit including the lower blade of switch S3, the armature and contact of relay R2", the winding of relay R2 andr'esistorZ 2. Similarly the operation, of relay Rs will cause the operation of relay R's; I -By opening switch S1 and closing switches S2 and S3 the operator may light any one of the lamps L1, L2 and In which are associated respectively with relays R'1, R2 and R's. By moving the rotary switch S4 to its contact I, the voltage across the secondary winding W4 of transformer T2 will be transmitted to the filament of lamp L1, the circuit including the winding W4, the movable. arm of switch S4 and the. lamp L1. By moving the-arm of switch S to its contact 2 the lamp L1 will be disconnected from the winding W4 of transformer T2 and extinguished and the lamp L2 will then be connected to the Winding W4 and illuminated. By further moving the switch S4 to. its contact 3, the lamp L2 will be disconnected from the circuit of winding W4 and the lamp L1,for example, being colored red, the lamp L2;amber, and the lamp L3 green. These three lamps will be used to indicate instantly the approximate level of the energy impressed upon the transmitter TR,. the lamp L1 indicating a low level-of impressed energy,'the lamp L2 a higher level, and the lamp L3 a still higher level.

Suppose, now, that switch S1 is closed so as to connect the transmitter TR to the primary Winding'of the transformer T1 and the circuit of the buzzer Y is then also completed. Assume also that the arm of switch S4 is moved to its contact 0. Now if the buzzer Y is held approximately three feet from the transmitter TR, the energy amplified by tube V and rectified by tubes V2 and V3 will beso low as to operate the relay R1 alone. The operation of relay R1 will in turn operate the relay R1, which in turn will cause the lamp L1 to be lit. The circuit of'lamp L1 will include the winding W4 of transformer T2, the armature and back contact of relay R's, the armature a'ndback contact of relay R2, the armature and make contact of relay R1 and lamp L1. The lamps L2 and L3 will remain unlit. If the lamp L1 is painted red as suggested above, it will indicate that the level of energy impressed upon the. transmitter TR, is insuflicient for good signal transmission. 3 If, now, the buzzer Y is moved closer to the transmitter'TR, the amplitude of the current flowing through the anode circuits of the rectifier tubes V2 and V3 will be such as to produce a sufficient voltage across resistor Z2 to operate the relay R2. The operation of relay R2 will then cause the operation'of relay R2 and thisin turn will light the amber lamp L2. The circuit of lamp L2 will include the Winding W4 of transformer T2, the armature and back contact of relay R's, the armature and make contact of relay R2 and lamp L2. The lamp L1 will, of course, become extinguished. The illumination of the lamp L2 will indicate that the level 'of energy impressed upon the transmitter TR is better, but this level of energy will still be insufficient for good signal-transmission.

If now, the buzzer Y is moved still closer to the transmitter TR, the magnitude of the rectified current flowing'through the resistor Z3 will produce such a voltage across its terminals as will be sufiicient to operate the relay R3. The opera-' -R'3 and this inturn' will illuminate the green lamp L3. The circuit of lamp L3 includes the secondary winding W4 of transformer T2 and the armature and make contact of relay R'3. The lamp 'L2 will at the same time be extinguished. The illumination of the green lamp L3 will indicate that the level of the energy impressed upon the transmitter TB is s uii icientfor good trans mission. This position of the buzzer Y withretransmitter '13 a suflicient distance, the lamp L3.

will become extinguished but the lamp L2 will be f illuminated, As the buzzerYis moved still'further away from the transmitter'TR the lamp L2 will become extinguished and the lamp L1 illuminated. Thus each one of the lamps L1, L2 and L3 will indicate, within certain limits, the level of the energy impressed upon the transmitter TR and if no energyis impressed upon transmitter TR, none of the lamps L1, L2 or L3 will be illuminated.

If the circuit of buzzer Yis now opened and speech is impressed upon the transmitter TR, the level of the rectified speech currents producedwill cause the lamps L1, L2 and L3 to become illuminated according to the magnitude of currents. If, for example, a loud tone isproduced close to the transmitter TR, the lamps L1, L2 and L3, 001- ored respectively red, amber and green, as already explained, will become illuminated successively.

If the tone is produced somewhat more distantly from the transmitter then the lamps L1 and L2,

the red and amber lamps, will be successively illuminated. If thetone is very soft or is very distant from the transmitter TR then only the red lamp L1 willbe lit. If the tone is not steady, the lamps will flash on and oil according to the durations of the tone pulses and frequency of the flashes will depend, of course, upon the nature ofthe words or phrases used as will be understood by those skilled in the art. Yet the average light impression, that is, the average time during which the green lamp L3 is on or the amber lamp L2 is on, etc., will determine whether the speech is good,;or only fair, or verypoor. Whenno speech currents are impressed on the transmitter TR then none of the lamps L1 L2 or L3 will be lighted,

as will be apparent to those skilled in the art.

The tone impressed upon the transmitter TR causes a variable current to flow through the primary winding of the transformer T1, This proto vary due to the alternating current voltage applied to the grid according to the customary ac tion of the vacuum tube amplifier circuits. The

amplified alternating current voltage transmitted to the secondary winding of the transformer T3 is then applied to both of the grid electrodes of the tubes V2 and V3, respectively. The grids of,

the latter tubes are both biased negatively with respect to their respective cathodes and will hence pass plate current only during the positive grid swings and then only in accordance with the gridvoltage plate-current characteristic curve of these rectifying tubes. The combined plate currents of both tubes V2 and V2 will then flow through the circuit of the milliammeter MA, resistors Z3 and Z2 and the winding of relay R1 and will operate relay R1. Yet if greater currents traverse the latamperes traversed the series circuit, relay R2 operated when .a current about 5 milliamperes traversed the circuit and relayRa at a currentof about 16 milliamperes.

I In the arrangement of the circuit tried out the generatorG' was the ordinary 110-115 volt,

voltage of about 5 volts and the winding W4.

a terminalvoltage of about 6.5 volts. The lowpass filter coil D was a Thordarson type T--13C- 29 coil-and the condensers C1 and C2 were of about 8 microfarads capacity. The potentiometer P was a 20,000 ohm Dividohrn device. The tube V1 Was'of a No. 56 type, tubes V2 and V3 were of the No. 45 type and tube V4. of the No.- 80 type. The condenser C4 had a capacity of about 8 microfarads'and the resistors Z2 and Z3 were approximately of 250' ohms and 100 ohms respectively.

It is apparent that the arrangement illustrated in the drawing maybe employed to visually indicate the proper and improper use. of

a telephone transmitter. The signals will especially indicate the proper distance required between the lips of the speaker and the telephone transmitter TR and/or the proper tone level for good transmission.

While this invention has. been scribed shown and dein certain particular arrangements merely for the purpose of illustration, it will be understood that the general principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and, the scope of the appended claims; What is claimed is: i

1. Apparatus for instantly indicating the magnitude of energy impressed upon a telephone transmitter, comprising -means for amplifying and detecting substantially all components of the energy impressed upon the transmitter a source of alternating current, a detector for detesting said alternating current, a potentiometer ,through which "the detected alternating current flows, a plurality of impedances connected in series with each other and with said potentiometer, the amplified and detected energy flowing throughsaid impedances, a plurality of relays the windings of which respectively shunt, said impedances, said relaysbeing adjusted to operate successively, the number of relays operated corresponding to the amount of energy amplilied and detected, and indicating means con- 1 trolled by said relays.

2. A system. for indicating to a speaker the amount of energy impressed upon a telephone transmitter, comprising means for detecting the energy impressed on the telephone transmitter, a source of alternating current, means for rectifying said alternating current, a plurality of impedances connected in series both with said energy. detecting means and said rectifying means, first and second groups of relays, the

windings of the relays of the first group respectively shunting said impedances, the relays of the second group being operated in response to the corresponding relays of the first group,

means for successively operating a predeter mined number of the relays of the first group,

eluding a plurality of impedances connected in series with each other and with said rectifying means, the detected current flowing through said series impedances, a plurality of relays, the windings of which respectively shunt said 'impedances, said relays operating successively, the number of relays successively operated corresponding to the magnitude of the detected cur-, rent, and indicating means controlled by said relays, said indicating means being operated by said alternating current. V

SAMUEL BETTLEHUGHES1 

